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There is an urgent need for effective therapeutic interventions against SARS-CoV-2, including new variants that continue to arise. Neutralizing monoclonal antibodies have shown promise in clinical studies. We investigated the therapeutic efficacy of a combination of two potent monoclonal antibodies, C135-LS and C144-LS that carry half-life extension mutations, in the rhesus macaque model of COVID-19. Twelve young adult macaques (three groups of four animals) were inoculated intranasally and intra-tracheally with a high dose of SARS-CoV-2 and 24 hours later, treated intravenously with a high (40 mg/kg) or low (12 mg/kg) dose of the C135-LS and C144-LS antibody combination, or a control monoclonal antibody. Animals were monitored for 7 days. Compared to the control animals, animals treated with either dose of the anti-SARS-CoV-2 antibodies showed similarly improved clinical scores, lower levels of virus replication in upper and lower respiratory tract, and significantly reduced interstitial pneumonia, as measured by comprehensive lung histology. In conclusion, this study provides proof-of-concept in support of further clinical development of these monoclonal antibodies against COVID-19 during early infection.

Human immunodeficiency virus (HIV)-1 assembly is initiated by Gag binding to the inner leaflet of the plasma membrane (PM). Gag targeting is mediated by its N-terminally myristoylated matrix (MA) domain and PM phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2]. Upon Gag assembly, envelope (Env) glycoproteins are recruited to assembly sites; this process depends on the MA domain of Gag and the Env cytoplasmic tail. To investigate the dynamics of Env recruitment, we applied a chemical dimerizer system to manipulate HIV-1 assembly by reversible PI(4,5)P2 depletion in combination with super resolution and live-cell microscopy. This approach enabled us to control and synchronize HIV-1 assembly and track Env recruitment to individual nascent assembly sites in real time. Single virion tracking revealed that Gag and Env are accumulating at HIV-1 assembly sites with similar kinetics. PI(4,5)P2 depletion prevented Gag PM targeting and Env cluster formation, confirming Gag dependence of Env recruitment. In cells displaying pre-assembled Gag lattices, PI(4,5)P2 depletion resulted in the disintegration of the complete assembly domain, as not only Gag but also Env clusters were rapidly lost from the PM. These results argue for the existence of a Gag-induced and -maintained membrane micro-environment, which attracts Env. Gag cluster dissociation by PI(4,5)P2 depletion apparently disrupts this micro-environment, resulting in the loss of Env from the former assembly domain. IMPORTANCE Human immunodeficiency virus (HIV)-1 assembles at the plasma membrane of infected cells, resulting in the budding of membrane-enveloped virions. HIV-1 assembly is a complex process initiated by the main structural protein of HIV-1, Gag. Interestingly, HIV-1 incorporates only a few envelope (Env) glycoproteins into budding virions, although large Env accumulations surrounding nascent Gag assemblies are detected at the plasma membrane of HIV-expressing cells. The matrix domain of Gag and the Env cytoplasmatic tail play a role in Env recruitment to HIV-1 assembly sites and its incorporation into nascent virions. However, the regulation of these processes is incompletely understood. By combining a chemical dimerizer system to manipulate HIV-1 assembly with super resolution and live-cell microscopy, our study provides new insights into the interplay between Gag, Env, and host cell membranes during viral assembly and into Env incorporation into HIV-1 virions. [ABSTRACT FROM AUTHOR]

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection produces B cell responses that continue to evolve for at least a year. During that time, memory B cells express increasingly broad and potent antibodies that are resistant to mutations found in variants of concern.sup.1. As a result, vaccination of coronavirus disease 2019 (COVID-19) convalescent individuals with currently available mRNA vaccines produces high levels of plasma neutralizing activity against all variants tested.sup.1,2. Here we examine memory B cell evolution five months after vaccination with either Moderna (mRNA-1273) or Pfizer-BioNTech (BNT162b2) mRNA vaccine in a cohort of SARS-CoV-2-naive individuals. Between prime and boost, memory B cells produce antibodies that evolve increased neutralizing activity, but there is no further increase in potency or breadth thereafter. Instead, memory B cells that emerge five months after vaccination of naive individuals express antibodies that are similar to those that dominate the initial response. While individual memory antibodies selected over time by natural infection have greater potency and breadth than antibodies elicited by vaccination, the overall neutralizing potency of plasma is greater following vaccination. These results suggest that boosting vaccinated individuals with currently available mRNA vaccines will increase plasma neutralizing activity but may not produce antibodies with equivalent breadth to those obtained by vaccinating convalescent individuals. Individual memory antibodies selected over time by natural infection with SARS-CoV-2 have greater potency and breadth than antibodies elicited by vaccination, whereas the overall neutralizing potency of plasma is greater following vaccination., Author(s): Alice Cho [sup.1] , Frauke Muecksch [sup.2] , Dennis Schaefer-Babajew [sup.1] , Zijun Wang [sup.1] , Shlomo Finkin [sup.1] , Christian Gaebler [sup.1] , Victor Ramos [sup.1] , Melissa [...]

More than one year after its inception, the coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains difficult to control despite the availability of several working vaccines. Progress in controlling the pandemic is slowed by the emergence of variants that appear to be more transmissible and more resistant to antibodies.sup.1,2. Here we report on a cohort of 63 individuals who have recovered from COVID-19 assessed at 1.3, 6.2 and 12 months after SARS-CoV-2 infection, 41% of whom also received mRNA vaccines.sup.3,4. In the absence of vaccination, antibody reactivity to the receptor binding domain (RBD) of SARS-CoV-2, neutralizing activity and the number of RBD-specific memory B cells remain relatively stable between 6 and 12 months after infection. Vaccination increases all components of the humoral response and, as expected, results in serum neutralizing activities against variants of concern similar to or greater than the neutralizing activity against the original Wuhan Hu-1 strain achieved by vaccination of naive individuals.sup.2,5-8. The mechanism underlying these broad-based responses involves ongoing antibody somatic mutation, memory B cell clonal turnover and development of monoclonal antibodies that are exceptionally resistant to SARS-CoV-2 RBD mutations, including those found in the variants of concern.sup.4,9. In addition, B cell clones expressing broad and potent antibodies are selectively retained in the repertoire over time and expand markedly after vaccination. The data suggest that immunity in convalescent individuals will be very long lasting and that convalescent individuals who receive available mRNA vaccines will produce antibodies and memory B cells that should be protective against circulating SARS-CoV-2 variants. Antibodies against SARS-CoV-2 continue to evolve 6 to 12 months after infection in patients who have recovered from COVID-19, increasing in potency and breadth with time., Author(s): Zijun Wang [sup.1] , Frauke Muecksch [sup.2] , Dennis Schaefer-Babajew [sup.1] , Shlomo Finkin [sup.1] , Charlotte Viant [sup.1] , Christian Gaebler [sup.1] , Hans- Heinrich Hoffmann [sup.3] , [...]

Neutralizing antibodies that target the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein are among the most promising approaches against COVID-19.sup.1,2. A bispecific IgG1-like molecule (CoV-X2) has been developed on the basis of C121 and C135, two antibodies derived from donors who had recovered from COVID-19.sup.3. Here we show that CoV-X2 simultaneously binds two independent sites on the RBD and, unlike its parental antibodies, prevents detectable spike binding to the cellular receptor of the virus, angiotensin-converting enzyme 2 (ACE2). Furthermore, CoV-X2 neutralizes wild-type SARS-CoV-2 and its variants of concern, as well as escape mutants generated by the parental monoclonal antibodies. We also found that in a mouse model of SARS-CoV-2 infection with lung inflammation, CoV-X2 protects mice from disease and suppresses viral escape. Thus, the simultaneous targeting of non-overlapping RBD epitopes by IgG-like bispecific antibodies is feasible and effective, and combines the advantages of antibody cocktails with those of single-molecule approaches. The bispecific IgG1-like CoV-X2 prevents SARS-CoV-2 spike binding to ACE2, neutralizes SARS-CoV-2 and its variants of concern, protects against disease in a mouse model, whereas the parental monoclonal antibodies generate viral escape., Author(s): Raoul De Gasparo [sup.1] , Mattia Pedotti [sup.1] , Luca Simonelli [sup.1] , Petr Nickl [sup.2] , Frauke Muecksch [sup.3] , Irene Cassaniti [sup.4] , Elena Percivalle [sup.4] , [...]

Here we report on the antibody and memory B cell responses of a cohort of 20 volunteers who received the Moderna (mRNA-1273) or Pfizer-BioNTech (BNT162b2) vaccine against SARS-CoV-2.sup.1-4. Eight weeks after the second injection of vaccine, volunteers showed high levels of IgM and IgG anti-SARS-CoV-2 spike protein (S) and receptor-binding-domain (RBD) binding titre. Moreover, the plasma neutralizing activity and relative numbers of RBD-specific memory B cells of vaccinated volunteers were equivalent to those of individuals who had recovered from natural infection.sup.5,6. However, activity against SARS-CoV-2 variants that encode E484K-, N501Y- or K417N/E484K/N501-mutant S was reduced by a small--but significant--margin. The monoclonal antibodies elicited by the vaccines potently neutralize SARS-CoV-2, and target a number of different RBD epitopes in common with monoclonal antibodies isolated from infected donors.sup.5-8. However, neutralization by 14 of the 17 most-potent monoclonal antibodies that we tested was reduced or abolished by the K417N, E484K or N501Y mutation. Notably, these mutations were selected when we cultured recombinant vesicular stomatitis virus expressing SARS-CoV-2 S in the presence of the monoclonal antibodies elicited by the vaccines. Together, these results suggest that the monoclonal antibodies in clinical use should be tested against newly arising variants, and that mRNA vaccines may need to be updated periodically to avoid a potential loss of clinical efficacy. The Moderna (mRNA-1273) and Pfizer-BioNTech (BNT162b2) vaccines elicit anti-RBD antibodies similar to those elicited through natural infection with SARS-CoV-2, but their potent neutralizing activity was reduced or abolished by new viral variants of concern., Author(s): Zijun Wang [sup.1] , Fabian Schmidt [sup.2] , Yiska Weisblum [sup.2] , Frauke Muecksch [sup.2] , Christopher O. Barnes [sup.3] , Shlomo Finkin [sup.1] , Dennis Schaefer-Babajew [sup.1] , [...]

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected 78 million individuals and is responsible for over 1.7 million deaths to date. Infection is associated with the development of variable levels of antibodies with neutralizing activity, which can protect against infection in animal models.sup.1,2. Antibody levels decrease with time, but, to our knowledge, the nature and quality of the memory B cells that would be required to produce antibodies upon reinfection has not been examined. Here we report on the humoral memory response in a cohort of 87 individuals assessed at 1.3 and 6.2 months after infection with SARS-CoV-2. We find that titres of IgM and IgG antibodies against the receptor-binding domain (RBD) of the spike protein of SARS-CoV-2 decrease significantly over this time period, with IgA being less affected. Concurrently, neutralizing activity in plasma decreases by fivefold in pseudotype virus assays. By contrast, the number of RBD-specific memory B cells remains unchanged at 6.2 months after infection. Memory B cells display clonal turnover after 6.2 months, and the antibodies that they express have greater somatic hypermutation, resistance to RBD mutations and increased potency, indicative of continued evolution of the humoral response. Immunofluorescence and PCR analyses of intestinal biopsies obtained from asymptomatic individuals at 4 months after the onset of coronavirus disease 2019 (COVID-19) revealed the persistence of SARS-CoV-2 nucleic acids and immunoreactivity in the small bowel of 7 out of 14 individuals. We conclude that the memory B cell response to SARS-CoV-2 evolves between 1.3 and 6.2 months after infection in a manner that is consistent with antigen persistence. In a cohort of 87 individuals with COVID-19, the memory B cell response at 6.2 months after the onset of disease evolves in a manner that is consistent with the persistence of SARS-CoV-2 antigen., Author(s): Christian Gaebler [sup.1] , Zijun Wang [sup.1] , Julio C. C. Lorenzi [sup.1] , Frauke Muecksch [sup.2] , Shlomo Finkin [sup.1] , Minami Tokuyama [sup.3] , Alice Cho [sup.1] [...]

During the coronavirus disease-2019 (COVID-19) pandemic, severe acute respiratory syndrome-related coronavirus-2 (SARS-CoV-2) has led to the infection of millions of people and has claimed hundreds of thousands of lives. The entry of the virus into cells depends on the receptor-binding domain (RBD) of the spike (S) protein of SARS-CoV-2. Although there is currently no vaccine, it is likely that antibodies will be essential for protection. However, little is known about the human antibody response to SARS-CoV-2.sup.1-5. Here we report on 149 COVID-19-convalescent individuals. Plasma samples collected an average of 39 days after the onset of symptoms had variable half-maximal pseudovirus neutralizing titres; titres were less than 50 in 33% of samples, below 1,000 in 79% of samples and only 1% of samples had titres above 5,000. Antibody sequencing revealed the expansion of clones of RBD-specific memory B cells that expressed closely related antibodies in different individuals. Despite low plasma titres, antibodies to three distinct epitopes on the RBD neutralized the virus with half-maximal inhibitory concentrations (IC.sub.50 values) as low as 2 ng ml.sup.-1. In conclusion, most convalescent plasma samples obtained from individuals who recover from COVID-19 do not contain high levels of neutralizing activity. Nevertheless, rare but recurring RBD-specific antibodies with potent antiviral activity were found in all individuals tested, suggesting that a vaccine designed to elicit such antibodies could be broadly effective. Although rare, antibodies against the receptor-binding domain of SARS-CoV-2 that showed potent antiviral activity were obtained from all tested convalescent individuals, suggesting that a vaccine designed to elicit such antibodies could be broadly effective., Author(s): Davide F. Robbiani [sup.1] [sup.9] , Christian Gaebler [sup.1] , Frauke Muecksch [sup.2] , Julio C. C. Lorenzi [sup.1] , Zijun Wang [sup.1] , Alice Cho [sup.1] , Marianna [...]